Variable Time-Scale Streaming For Multimedia Transmission Over IP Networks

This paper presents an analysis of a rate adaptive multimedia streaming technique according to which rate changes are obtained by varying the inter-packet transmission interval, rather than altering the source coding rate. Instead of constraining the transmitter to operate in real-time, the time scale of the proposed packet scheduler can vary between zero when the network is congested, to as faster than real-time as the channel bandwidth allows when the network is lightly loaded. Simulation results comparing a TCP-friendly test implementation of the variable time-scale streaming (VTSS) approach with an <i> ideal</i> source rate-adaptive technique ---whose performance represents the upper bound of any transmission system based on source rate adaptation--- show that the VTSS approach delivers higher perceptual quality (up to 1.2 dB PSNR in the considered scenario) and reduced quality fluctuations, for a wide range of standard video sequences. The gains are even more pronounced when the proposed technique is compared to constant bit-rate transmission.